1. Field of the Invention
The present invention relates to a face identification technique which detects human faces from images taken by a camera and compares them with a previously registered face, thereby detecting a specific person.
2. Description of the Prior Art
In order to search for a specific person like a criminal on a wanted list, a system is available that videotapes an unspecified number of the general public and records their images by installing surveillance cameras in airports, stations, shopping centers, busy streets, and the like. In this system, videotaped images are recorded as they are or face images are exclusively recorded by being extracted from the videotaped images. In these methods, there is a problem since the face images of the people other than the specific person are also recorded, failing to protect their rights of portrait or piracy.
Therefore, there is a system now available according to which the face image of a person videotaped by a surveillance camera is compared with the face image of the specific person registered: the face image of a videotaped person is recorded if these face images match with each other, whereas when these face images do not match with each other, the face image of the videotaped person is abandoned. In this system, out of the face images videotaped, those which do not match with the face image of the registered specific person are not kept, thereby securing protection of their privacy.
However, in the above-described system, what is recorded is only the face image matching with the face image of the specific person, and other useful information including the dress and baggage of the specific person and the situation around him or her are lost. As a result, when there is a match and a responsible official rushes to the display monitor by a report or when recorded images are confirmed later, the absence of information other than his or her face makes it difficult to search for the specific person.
On the other hand, in order to protect individuals' privacy, there is an approach of applying a mosaic process on face images as described in Japanese Laid-Open Patent Application No. 2001-86407. However, in this patent application, skin color is detected from videotaped human images and a mosaic process is automatically applied to face images, which forces all face images videotaped to be applied with a mosaic process, thereby making it impossible to apply a mosaic process to the face images excluding the face image of the specific person.
Japanese Laid-open Patent Application No. 2000-216 also discloses privacy protection measures by applying a mosaic process to human body images. However, when the technique of this patent application is used to protect the privacy of the people other than the specific person, it is difficult to check the situation around the specific person, because the whole image of the specific person is applied with the mosaic process.